How do I access my home computer remotely if I have dynamic IP ?

I sometimes need to get remote access to my home PC (when I am on long holidays).

I had static IP from BE for years and never bothered to look around.. I know there is a thing called dynamic DNS. But from what I understood is that my router needs to support it.

I had TP-Link which had native support for few Dynamic DNS services. But the BT HH5 - I dont see it anywhere.. Looked on the web - people say the access is intentionally disabled..

So my question is - whats the easiest / cheapest way to access my PC without knowing the current IP address of the HH5 ?

(I dont need it often - may be a dozen days a year but this must 100% reliable - I work from home so if I need to access it it has to be done, otherwise I might as well break the holiday and fly back)..